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- Cardenas, Eduardo I, et al.
(författare)
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Munc18-2, not Munc18-1 or Munc18-3, regulates platelet exocytosis, hemostasis, and thrombosis
- 2019
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 294:13, s. 4784-4792
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Tidskriftsartikel (refereegranskat)abstract
- Platelet degranulation, a form of regulated exocytosis, is crucial for hemostasis and thrombosis. Exocytosis in platelets is mediated by SNARE proteins, and in most mammalian cells this process is controlled by Munc18 (mammalian homolog of C. elegans uncoordinated gene 18) proteins. Platelets express all Munc18 paralogs (Munc18‑1, ‑2, and ‑3), but their roles in platelet secretion and function have not been fully characterized. Using Munc18‑1, ‑2, and ‑3 conditional knockout mice, here we deleted expression of these proteins in platelets and assessed granule exocytosis. We measured products secreted by each type of platelet granule and analyzed EM platelet profiles by design-based stereology. We observed that removal of Munc18‑2 ablates release of alpha, dense, and lysosomal granules from platelets, but we found no exocytic role for Munc18‑1 or ‑3 in platelets. In vitro, Munc18‑2-deficient platelets exhibited defective aggregation at low doses of collagen and impaired thrombus formation under shear stress. In vivo, megakaryocyte-specific Munc18‑2 conditional knockout mice had a severe hemostatic defect and prolonged arterial and venous bleeding times. They were also protected against arterial thrombosis in a chemically-induced model of arterial injury. Taken together, our results indicate that Munc18‑2, but not Munc18‑1 or Munc18‑3, is essential for regulated exocytosis in platelets and platelet participation in thrombosis and hemostasis.
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- Cardenas, Eduardo I, et al.
(författare)
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Platelet Munc13-4 regulates hemostasis, thrombosis and airway inflammation.
- 2018
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Ingår i: Haematologica. - : Ferrata Storti Foundation (Haematologica). - 0390-6078 .- 1592-8721. ; 103:7, s. 1235-1244
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Tidskriftsartikel (refereegranskat)abstract
- Platelet degranulation is crucial for hemostasis and may participate in inflammation. Exocytosis in platelets is mediated by SNARE proteins and should be controlled by Munc13 proteins. We found that platelets express Munc13-2 and -4. We assessed platelet granule exocytosis in Munc13-2 and -4 global and conditional knockout (KO) mice, and observed that deletion of Munc13-4 ablates dense granule release and indirectly impairs alpha granule exocytosis. We found no exocytic role for Munc13-2 in platelets, not even in the absence of Munc13-4. In vitro, Munc13-4-deficient platelets exhibited defective aggregation at low doses of collagen. In a flow chamber assay, we observed that Munc13-4 acted as a rate-limiting factor in the formation of thrombi. In vivo, we observed a dose-dependency between Munc13-4 expression in platelets and both venous bleeding time and time to arterial thrombosis. Finally, in a model of allergic airway inflammation, we found that platelet-specific Munc13-4 KO mice had a reduction in airway hyper-responsiveness and eosinophilic inflammation. Taken together, our results indicate that Munc13-4-dependent platelet dense granule release plays essential roles in hemostasis, thrombosis and allergic inflammation.
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- Hoang, Oanh N, et al.
(författare)
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Mucins MUC5AC and MUC5B Are Variably Packaged in the Same and in Separate Secretory Granules.
- 2022
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Ingår i: American journal of respiratory and critical care medicine. - 1073-449X .- 1535-4970. ; 206:9, s. 1081-1095
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Tidskriftsartikel (refereegranskat)abstract
- Rationale: MUC5AC (mucin 5AC, oligomeric gel-forming) and MUC5B (mucin 5B, oligomeric gel-forming) are the predominant secreted polymeric mucins in mammalian airways. They contribute differently to the pathogenesis of various muco-obstructive and interstitial lung diseases, and their genes are separately regulated, but whether they are packaged together or in separate secretory granules is not known. Objectives: To determine the packaging of MUC5AC and MUC5B within individual secretory granules in mouse and human airways under varying conditions of inflammation and along the proximal-distal axis. Methods: Lung tissue was obtained from mice stimulated to upregulate mucin production by the cytokines IL-1β and IL-13 or by porcine pancreatic elastase. Human lung tissue was obtained from donated normal lungs, biopsy samples of transplanted lungs, and explanted lungs from subjects with chronic obstructive pulmonary disease. MUC5AC and MUC5B were labeled with antibodies from different animal species or, in mice only, by transgenic chimeric mucin-fluorescent proteins and imaged using widefield deconvolution or Airyscan fluorescence microscopy. Measurements and Main Results: In both mouse and human airways, most secretory granules contained both mucins interdigitating within the granules. Smaller numbers of granules contained MUC5B alone, and even fewer contained MUC5AC alone. Conclusions: MUC5AC and MUC5B are variably stored both in the same and in separate secretory granules of both mice and humans. The high fraction of granules containing both mucins under a variety of conditions makes it unlikely that their secretion can be differentially controlled as a therapeutic strategy. This work also advances knowledge of the packaging of mucins within secretory granules to understand mechanisms of epithelial stress in the pathogenesis of chronic lung diseases.
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- Rodarte, Elsa M, et al.
(författare)
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Munc13 proteins control regulated exocytosis in mast cells.
- 2018
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 293:1, s. 345-358
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Tidskriftsartikel (refereegranskat)abstract
- Mast cells (MCs) are involved in host defenses against pathogens and inflammation. Stimulated MCs release substances stored in their granules via regulated exocytosis. In other cell types, Munc13 (mammalian homolog of Caenorhabditis elegans uncoordinated gene 13) proteins play essential roles in regulated exocytosis. Here, we found that MCs express Munc13-2 and -4, and we studied their roles using global and conditional knock-out (KO) mice. In a model of systemic anaphylaxis, we found no difference between WT and Munc13-2 KO mice, but global and MC-specific Munc13-4 KO mice developed less hypothermia. This protection correlated with lower plasma histamine levels and with histological evidence of defective MC degranulation but not with changes in MC development, distribution, numbers, or morphology. In vitro assays revealed that the defective response in Munc13-4-deficient MCs was limited to regulated exocytosis, leaving other MC secretory effector responses intact. Single cell capacitance measurements in MCs from mouse mutants differing in Munc13-4 expression levels in their MCs revealed that as levels of Munc13-4 decrease, the rate of exocytosis declines first, and then the total amount of exocytosis decreases. A requirement for Munc13-2 in MC exocytosis was revealed only in the absence of Munc13-4. Electrophysiology and EM studies uncovered that the number of multigranular compound events (i.e. granule-to-granule homotypic fusion) was severely reduced in the absence of Munc13-4. We conclude that although Munc13-2 plays a minor role, Munc13-4 is essential for regulated exocytosis in MCs, and that this MC effector response is required for a full anaphylactic response.
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- Younan, George, et al.
(författare)
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The inflammatory response after an epidermal burn depends on the activities of mouse mast cell proteases 4 and 5
- 2010
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 185:12, s. 7681-7690
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Tidskriftsartikel (refereegranskat)abstract
- A second-degree epidermal scald burn in mice elicits an inflammatory response mediated by natural IgM directed to nonmuscle myosin with complement activation that results in ulceration and scarring. We find that such burn injury is associated with early mast cell (MC) degranulation and is absent in WBB6F1-Kit(W)/Kit(Wv) mice, which lack MCs in a context of other defects due to a mutation of the Kit receptor. To address further an MC role, we used transgenic strains with normal lineage development and a deficiency in a specific secretory granule component. Mouse strains lacking the MC-restricted chymase, mouse MC protease (mMCP)-4, or elastase, mMCP-5, show decreased injury after a second-degree scald burn, whereas mice lacking the MC-restricted tryptases, mMCP-6 and mMCP-7, or MC-specific carboxypeptidase A3 activity are not protected. Histologic sections showed some disruption of the epidermis at the scald site in the protected strains suggesting the possibility of topical reconstitution of full injury. Topical application of recombinant mMCP-5 or human neutrophil elastase to the scalded area increases epidermal injury with subsequent ulceration and scarring, both clinically and morphologically, in mMCP-5-deficient mice. Restoration of injury requires that topical administration of recombinant mMCP-5 occurs within the first hour postburn. Importantly, topical application of human MC chymase restores burn injury to scalded mMCP-4-deficient mice but not to mMCP-5-deficient mice revealing nonredundant actions for these two MC proteases in a model of innate inflammatory injury with remodeling.
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